In a principal aspect, the present invention relates to an improved supplementary heat control for a heat pump system and more particularly to a supplementary control adapted to sense heat requirements and initiate input of supplementary heat to the system.
Heat pump systems are popular in regions of the country wherein temperature extremes, particularly cold temperature extremes, do not frequently occur. When in the heating cycle, the condensor coil of a heat pump assembly is utilized to discharge heat into a moving air stream. Thus, cool air is withdrawn from the enclosure, is heated by passage over the condensor coil and is subsequently ejected into the enclosure.
Whenever heating demand exceeds the capacity of the heat pump, supplementary heat must be provided to the air stream. Such supplementary heat may be provided by any of a number of sources, including electric resistance heat, hot water heat, a fossil fuel source, a fired heat exchanger or other available sources. Commonly, the need for supplementary heat is sensed and the control of such heat is provided by thermostatic control means situated in the enclosure being heated. Alternatively, the temperature outside the enclosure is sensed and compared in some fashion with the temperature in the enclosure to determine whether a supplementary heat source must be utilized. Such arrangements often are complex and require a skilled craftsman for installation.
Thus, an apparatus and method which provides control for variable supplementary heat requirements is desired. Additionally, a system which eliminates the need for outside thermostats and wiring is needed. Finally, a supplementary heat control system which will facilitate and improve the warm-up capability of a heat pump system is desirable.